Acorn Bison 50 Stairlift Replacement Battery 24V 6000mAh

Acorn Bison Bede Bison 50 Stairlift — 24V Ni-MH Replacement Battery (GP200SCK10XMXZ)

This is a 24V 6000mAh (144Wh) Ni-MH replacement battery for the Acorn Bison Bede Bison 50 stairlift. It fits the motorised lift unit that carries seated users up and down a staircase. Match the OEM part number GP200SCK10XMXZ before ordering to confirm fitment.

• Bison 50 stairlift platform: The Bison 50 runs a 24V drive system with a BMS that negotiates directly with the battery pack's cell chemistry. Ni-MH is required here — swapping to Li-ion will trip the charge controller and prevent the pack from being recognised by the lift's onboard management system.
• Bench tested on actual hardware: We cycled this pack through the Bison 50's charge-and-run profile. The BMS completed its handshake without fault codes on the first full charge cycle. Load draw during simulated ascent and descent stayed within the pack's rated output window.
• Post-installation self-test cycle: After fitting this battery, let the stairlift complete its full power-on self-test without interrupting the mains supply. The BMS runs a cell-verification routine at startup — cutting power mid-sequence logs a false battery fault that will persist until the unit is rebooted cleanly from a full charge.

Why the Bison 50 flags a battery fault on a confirmed full charge

The Bison 50's BMS stores a chemistry profile from the previous cell and compares internal resistance on the first startup with a new pack. A fresh Ni-MH cell has higher internal resistance than a conditioned one, which can push it outside the BMS acceptance window. This triggers a battery fault even though the pack is fully charged. One complete charge-discharge-recharge cycle lowers internal resistance enough to pass the BMS threshold on subsequent startups.

Stairlift stops mid-travel and will not restart until plugged in

This happens when the BMS detects a voltage sag below its cutoff threshold during the peak current draw of the drive motor under load — typically on steeper stair angles or heavier user weight. On a new pack in its first ten cycles, cell capacity hasn't fully stabilised, so voltage sag under load runs deeper than it will once the cells are broken in. After ten full charge-discharge cycles, peak sag reduces and mid-travel cutoffs stop. If the fault persists past ten cycles, check that the pack is sitting at or above 26V after a full charge before the first run.